Environmental surveillance of poliovirus in Italy: pilot study

A pilot study on environmental surveillance of poliovirus included one hundred ninety-six samples (drinking water, surface water, seawater and sewage), collected between 1996 and 1998 in different regions of Italy. Samples were screened for the presence of poliovirus and other enteric viruses. Twelve polioviruses, 35 non polio enteroviruses (NPE) and 51 enteric non entero (NE) viruses were isolated. All poliovirus isolates, namely four type 1, four type 2 and four type 3, were characterised as Sabin-like strains. Thirty-one Coxsackie B and 4 Echo viruses were also detected. The presence of Sabin-like polioviruses in the environment is not unexpected since immunization with only oral poliovirus vaccine was performed in Italy until May 1999, when a sequential schedule consisting of two doses of inactivated polio vaccine (IPV) and two of oral polio vaccine (OPV) was adopted; in July 2002 a schedule consisting of four doses of IPV was adopted. Although this is only a pilot study and the number of samples analysed is limited, so far data from this study so far supports once again evidence of lack of circulating wild poliovirus and is in line with results from AFP surveillance in Italy and stool survey on healthy children.